Control apparatus and a control method for a vehicle

ABSTRACT

A control device and a control method capable of eliminating a torque variation in changing an air/fuel ratio and establishing a compatibility of promotion in fuel economy with promotion in drivability is provided. The device includes an outer environment detector for detecting an outer environment in running a vehicle, a running environment determining device for predicting a current running environment in accordance with the outer environment, a data storage device for storing data for changing a driving characteristic, a selecting device for selecting the data, a control quantity calculator for calculating a control quantity based on the data, and a control actuator for controlling a control object. The engine output is efficiently utilized since the air/fuel ratio is changed in accordance with the change in the running environment, and the fuel cost reduction and the promotion of the drivability can be achieved since the selecting of the air/fuel ratio is performed in accordance with the running environment.

This application is a continuation of application Ser. No. 08/816,703,filed Mar. 13, 1997, now U.S. Pat. No. 5,724,944, which is acontinuation of application Ser. No. 08/695,345, filed Aug. 9, 1996, nowU.S. Pat. No. 5,638,790, which is a continuation of application Ser. No.08/365,444, filed Dec. 28, 1994, which is now abandoned.

FIELD OF THE INVENTION

This invention relates to a control apparatus and a control method for amotor vehicle, and, in particular, to a control apparatus and a controlmethod for a motor vehicle for efficiently controlling an engine powertrain in accordance with various information such as a runningenvironment of the motor vehicle and the like.

BACKGROUND OF THE INVENTION

A known conventional control system, for instance, as disclosed inJapanese Patent Laid Open No. Sho 62-126235, determines an operatingregion in accordance with a change in an operating state, that is, achange in an engine load (pressure in the intake pipe, air/fuel ratiosensor signal or the like) and a change in an engine rotational speed,for establishing compatibility between fuel economy and drivability, andreads a target air/fuel ratio value which has been set for everyoperating region, thereby changing the air/fuel ratio of an engine.

When the target air/fuel ratio is changed with the engine load and theengine rotational speed as parameters as in the conventional technology,a steady state condition is changed to another steady state condition.The fuel quantity is then changed during acceleration of the vehicle bywhich a torque variation is generated. This produces a strange feelingfor the vehicle operator since the fuel quantity is changed during theacceleration. Further, when a NOx reduction catalyst is not employed,the air/fuel ratio considerably changes from an air/fuel ratio of 14.7,which is the theoretical mixture ratio, to around an air/fuel ratio of24 for reducing a discharge quantity of NOx, by which the torquevariation is further increased.

SUMMARY OF THE INVENTION

There is therefore needed a control apparatus and a control methodcapable of achieving compatibility between promoting the fuel economyand the drivability by eliminating torque variations which occur inchanging the air/fuel ratio during a running operation of a motorvehicle.

These needs are met according to the present invention which provides acontrol apparatus and method including an outer environment detector fordetecting the outer environment during the running of the motor vehicle,a running environment determining system for predicting a currentrunning environment, for instance, a road incline, a road with a trafficjam, and the like, in accordance with the outer environment, a datastoring device for storing data used to change an operatingcharacteristic in accordance with the running environment, a switchingsystem for switching the data in accordance with the runningenvironment, a control quantity calculator for calculating a controlquantity based on the data selected from the data storing device and acontrol actuator for controlling a control object. These systems can beimplemented in either a hardware circuit, or as software applicationsoperating on a microprocessor or the like.

It is an advantage of the present invention, constructed as describedabove, that the data, such as the air/fuel ratio or the like, is alwaysswitched taking into consideration the running environment in anon-steady state condition, a speed changing condition, a stoppingcondition, an idling condition, a operation of a shift lever, and thelike. Therefore, any unpleasant feeling for the driver due to the torquevariation accompanied by the change in the air/fuel ratio is eliminated.Accordingly, a reduction in the actual fuel cost and a promotion of thedrivability can both be achieved.

A detailed explanation will be given to embodiments of the presentinvention based on the drawings as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an embodiment of the control system of thepresent invention;

FIG. 2 is a block diagram illustrating an example of the construction ofa specific control system according to the embodiment in FIG. 1;

FIG. 3 is a block diagram wherein control of an air flow quantity isadded to the fuel control system illustrated in FIG. 2;

FIG. 4 is a conceptual diagram illustrating a specific example of theswitching of an air/fuel ratio;

FIG. 5 illustrates an example of a correction table diagram of a targetair/fuel ratio;

FIG. 6 is a control flow chart diagram illustrating the operation of thepresent invention for a motor vehicle running in a traffic jam;

FIG. 7 is a control flow chart diagram continued from FIG. 6;

FIG. 8 is a control flow chart diagram illustrating the operation ofcontrolling an air flow quantity;

FIG. 9 is a conceptual block diagram illustrating a construction of thepresent invention in a motor vehicle;

FIG. 10 is a control flow chart diagram illustrating the operation of anair/fuel ratio switching control;

FIG. 11 is a control flow chart diagram illustrating the operation ofthe present invention for a motor vehicle running in the overlappingconditions of a traffic jam and/or an uphill or a downhill slope; and

FIG. 12 is a correlation diagram illustrating a relationship between theroad incline in a traffic jam and a corrected air/fuel ratio.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an embodiment of the control system of thepresent invention. First, signals or images from an outer environmentdetector 1 for detecting conditions of an outer environment during therunning of a motor vehicle, are input to a running environmentdetermining system 2 in a controller 41. The running environmentdetermining system 2 predicts the current running environment for themotor vehicle, for instance, a road incline, a traffic jam on a road,and the like, in accordance with the signals detected by the outerenvironment detector 1. Next, a data storing device 3 stores data usedto change an operating characteristic in accordance with the runningenvironment. A switching system 4 selects the data in the data storingdevice 3 based on the environment which has been determined by therunning environment determining system 2. A control quantity calculator5 calculates a control quantity based on the selected data, and outputsthe control quantity to a control actuator 6, thereby controlling acontrol object, such as the engine, transmission, or the like.

FIG. 2 is a specific example of the embodiment illustrated in FIG. 1. Asin FIG. 1, signals or images from the outer environment detector 1 fordetecting the outer environment in the running of a motor vehicle areinput to the running environment determining system 2, and the currentrunning environments, for instance, a road incline, a traffic jam on aroad, or the like, are predicted in accordance with the outerenvironment. Next, a corrected air/fuel ratio storing device 7 storescorrected air/fuel ratios in accordance with a plurality of runningenvironment conditions. These corrected air/fuel ratios are switched bythe switching system 4, and a desired air/fuel ratio of an engine isachieved in accordance with the current running environment. Further, afuel quantity calculator 8 receives values which have been calculated bythe corrected air/fuel ratio storing device 7 and a basic fuel quantitycalculator 9. The basic fuel quantity is normally calculated by an airflow quantity and the engine rotational speed. The final calculation offuel quantity is performed by calculating a correction coefficient basedon the data of the corrected air/fuel ratio storing device 7 andmultiplying or adding the coefficient to the basic fuel quantity.Further, the calculated value is output to the fuel injection valve 13based on a reference signal of engine rotational speed.

FIG. 3 is a control block diagram in which the fuel control illustratedby FIG. 2 further includes an air flow quantity control. The fuelinjection valve control is the same as in FIG. 2. Further, a targeteddriving shaft torque calculator 11 detect input signals and calculates atargeted driving shaft torque which is required by a driver usingsignals of the accelerator opening position α, a vehicle speed Vsp, andthe like. The targeted engine torque calculator 12 calculates a targetedengine torque using the targeted driving shaft torque, a torqueconverter characteristic of the transmission, an engine characteristic,and the like, and further based on the data from the corrected air/fuelratio storing device 7. Next, a throttle opening position calculator 13calculates a targeted opening position for the throttle based on thetargeted engine torque, the engine rotational speed, and the like. Thetargeted opening position is output to a throttle control valve 14,which is electronically controlled by a motor or the like. Accordingly,the addition of this air flow quantity control can correct the enginetorque which changes by a change in the air/fuel ratio, by the air flowquantity, thereby promoting the drivability of the motor vehicle.

FIG. 4 illustrates a specific example of the switching of the air/fuelratio. In detecting the outer environment, first, one method makes useof outer infrastructure information such as information gathered fromdisplay boards installed on the roads or road information gathered by anFM multiplex transmitter. Second, another method detects outerenvironment information using an outer vehicle environment recognizingsensor, such as a TV or video camera, provided inside the vehicle. Athird method makes use of the processed data and operating signals of avehicle (for instance, vehicle speed, output shaft torque etc.). Fordetecting the outer environment, a combination of the methods describedabove, or an individual method, may be used. The method to be used canbe determined in accordance with the detection accuracy and thecircumstances of the application. Next, the running environment isdetermined.

This includes information on the road incline, such as an uphill ordownhill, if a traffic jam is present, the steady state or theacceleration state of an expressway, a city traffic driving situation,and the like. These outer running environment conditions are provided bythe outer environment detector. Further, an air/fuel ratio is selectedin switching the air/fuel ratio. The selected air/fuel ratio achievescompatibility between the drivability and the fuel economy according tothe running environment. For instance, in case of an uphill road inclineand an expressway acceleration, the air/fuel ratio needs a rich mixtureratio of about 13. This is because there is a high probability thatmaximum engine output is required. Further, in the case of a downhillroad incline, a traffic jam, or steady state condition on an expressway,the air/fuel ratio is determined to be a lean mixture ratio ofapproximately 24. This is because a high engine output is not necessary,thereby achieving a considerable reduction in the fuel cost. Further,for the case of normal running in a city area or the like, the air/fuelratio is determined to be at the theoretical mixture ratio of 14.7.

As shown in FIG. 5, a correction table for the air/fuel ratio is shownwith the engine rotational speed Ne as the abscissa and the basic fuelinjection width Tp as the ordinate. In the region of a low enginerotational speed including the idling state, and a low basic fuelinjection width, the air/fuel ratio is determined such that thecombustion is stabilized. For example, when better engines aredeveloped, the engines can be driven by a leaner mixture.

FIGS. 6 and 7 are control flow charts illustrating the operation of thecontrol system for a motor vehicle operating in a traffic jam on a road.First, in step 15, the control system reads a forward intervehicledistance Sf, a rearward intervehicle distance Sr, a vehicle speed Vsp, abasic fuel injection width Tp and an engine rotational speed Ne. In step16, the operation calculates a timewise change ΔSf of the forwardvehicle distance by the following equation (Equation 1):

    ΔSf= Sf(n)-Sf(n-1)!/ T(n)-T(n-1)!                    (Equation 1)

In step 17, the operation calculates a timewise change ΔSr of therearward intervehicle distance by the following equation (Equation 2):

    ΔSr= Sr(n)-Sr(n-1)!/ T(n)-T(n-1)!                    (Equation 2)

In step 18, the operation calculates the acceleration G of the drivingvehicle by the following equation (Equation 3):

    G= Vsp(n)-Vsp(n-1)!/ T(n)-T(n-1)!                          (Equation 3)

In step 19, the operation calculates the mean vehicle speed Vave of thedriving vehicle by the following equation (Equation 4):

    Vave(n)= Vsp(n)+ . . . +Vsp(n-k)!/(k+1)                    (Equation 4)

Further, in step 20, the operation performs a count for memorizing themean vehicle speed Vave(n-a) of "a" times before. That is, the operationdetermines whether "x" equals "a". If "x" is not "a", the operation adds1 to "x" in step 21 and proceeds to step 24 in FIG. 7. If "x" equals"a", the operation substitutes the mean vehicle speed Vave (n-a) of "a"times before, by Vave(n) in step 22, and nullifies "x" in step 23. Next,in step 24 in FIG. 7, the operation determines whether the timewisechange ΔSf of the forward intervehicle distance which has beencalculated in accordance with Equation 1 is not larger than, forinstance, 10 m/s. That is, when the timewise change ΔSf is large, it isconsidered that the preceding vehicle has abruptly started and there isa high probability of there being no vehicle in front of the precedingvehicle. In step 25, the operation checks the timewise change of therearward intervehicle distance as in step 24, and determines whether thedriving vehicle is being squeezed by the forward and rearward vehiclesdue to the traffic jam. In step 26, the operation compares theacceleration G of the driving vehicle. When the forward direction isstagnated, in starting the driving vehicle, the starting acceleration islimited, and the operation determines there is a high probability of atraffic jam in a case wherein the acceleration is not larger than, forinstance, 0.5 q. Finally, in step 27, the operation employs the valuewhich has been calculated in step 22, and determines whether the meanvehicle speed Vave(n-a) of "a" times before, is not larger than, forinstance, 5 km/h. If the mean vehicle speed of the preceding severalseconds is not larger than 5 km/h, the operation determines that thestate wherein the vehicle speed is not greater than 5 km/h has continuedfor a while, that is, there is a high probability of a traffic jam.Accordingly, the operation performs an overall estimation of thejudgments made from step 24 to step 27, and determines the traffic jamwhen all the judgments are satisfied, and then proceeds to step 28.Further, when any one of steps 24 through 27 is No, the operationproceeds to step 29 and employs the corrected air/fuel ratio table ofthe running environment which has been determined in the precedingoperation. In step 28, since the traffic jam has been determined, theoperation selects a lean mixture of 24 for the air/fuel ratio in thecorrected air/fuel ratio table. Further, in step 30, the operationcalculates a corrected fuel injection coefficient k1 by a functionh(A/F) of the air/fuel ratio in step 28. In step 31, the control systemcalculates a fuel injection width Ti by the basic fuel injection widthTp and the corrected fuel injection coefficient k1 and outputs it instep 32.

FIG. 8 is a control flow chart illustrating the operation of controllingan air flow quantity. In a previously known technique, the enginerotational speed Ne and a turbine rotational speed Nt of the torqueconverter are detected, and a driving shaft torque Tt is calculated,from which the engine is then controlled. In this known method, thedriving shaft torque Tt doesn't become the required torque, because acontrolling amount for the engine is supplied using a value of thedriving shaft torque Tt without using a real engine torque Te.Therefore, the engine is not controlled by the most suitable value. Inaccordance with the present invention, at first a required targeteddriving shaft torque Ttar is decided, and a required targeted enginetorque Tet is calculated. Then, the engine is controlled as the realengine torque Te becomes the targeted engine torque Tet. In this method,the engine is controlled by the most suitable value, because the realengine torque Te is controlled directly as it becomes the targetedengine torque Tet. As shown with respect to FIG. 8, first, in step 33,the control system reads the accelerator opening position α, the vehiclespeed Vsp, the engine rotational speed Ne, the turbine rotational speedNt, the corrected air/fuel ratio A/F, and a change-gear ratio i.Thereafter, in step 34, the targeted driving shaft torque calculator 11(FIG. 3) calculates the targeted driving shaft torque Ttar using afunction f1 (α, Vsp) of the accelerator opening position α and thevehicle speed Vsp. In step 35, the targeted engine torque calculator 12calculates the targeted engine torque Tet using a function f2(Ttar, Ne,Nt, i, c, λ) of the targeted driving shaft torque Ttar, the enginerotational speed Ne, the turbine rotational speed Nt, the change-gearratio i, a characteristic ratio c of the torque converter, and a torqueratio λ of the torque converter. In step 36, the throttle openingposition calculator 13 calculates the targeted opening position θt forthe throttle using a function f3 (Tet, Ne, A/F) of the targeted enginetorque Tet, the engine rotational speed Ne, and the corrected air/fuelratio A/F. Then, in step 37, the control system supplies control signalsto the fuel injection valve 10.

FIG. 9 shows a system construction diagram of the present invention. Anengine 39 and a transmission 40 are mounted on a car body 38. An airflow quantity, a fuel quantity, an ignition timing, a speed changereduction ratio and the like are controlled by signals from an enginepower train controller 41. An intake port injection system of aconventionally known type, an inner cylinder injection system having agood control performance, or the like, is employed in the fuel control.Further, TV or video cameras 42 for detecting the outer environment andan antenna 43 for detecting the infrastructure information are mountedon the car body 38. Images of the TV cameras 42 are input into a runningenvironment determining system 44 and are image-processed, therebyrecognizing forward and backward intervehicle distances, traffic signalinformation, traffic signs and a road state condition. Further, theantenna 43 is connected to an infrastructure information receiver 45.Traffic jam information, information regarding a traffic accident,current position information of the vehicle in relation to thesurrounding infrastructure, are input from the infrastructureinformation receiver 45 to a running environment determining system 44.Further, map information, which has been stored in a CD-ROM 46 or thelike, is input to the running environment determining system 44. Thecurrent running environment is determined by the infrastructureinformation and the map information. A signal corresponding to therunning information is output from the running environment determiningsystem 44 and is input to the engine power train controller 41. The airflow quantity, the fuel quantity, the speed change reduction ratio, andthe like, corresponding to the running environment are controlled basedon the signal. Further, the throttle opening position θ, a signalindicative of speed changing operation FlgI, the vehicle speed Vsp, thegear shift lever switch signal Isw and the like are input to the enginepower train controller 41, which are employed for changing controlquantities, determining the running environment and the like.

FIG. 10 is a control flow chart of an air/fuel ratio switching control.In this invention, it is necessary to change the air/fuel ratio inaccordance with the running environment. It is possible to prevent thetorque variation due to the change in the air/fuel ratio by performingthe change of the air/fuel ratio in synchronism with, for instance,stopping, speed changing, idling or the like. First, in step 50, thecontrol system reads the corrected air/fuel ratio A/F, the throttleopening position θ, the gear shift lever switch signal Isw and thesignal indicative of speed change operation FlgI. In step 51, thecontrol system determines whether the current corrected air/fuel ratioof A/F(n) equals to the preceding corrected air/fuel ratio A/F(n-1).When the current corrected air/fuel ratio equals to the precedingcorrected air/fuel ratio, the control system proceeds to step 52,calculates the corrected fuel injection coefficient k1 by f4 A/F(n-1)!and holds the preceding air/fuel ratio. Further, the control systemcarries out A/F(n-1)=A/F(n-1) and outputs the corrected fuel injectioncoefficient k1 which has been calculated in step 52, in step 54.Further, when the current corrected air/fuel ratio A/F(n) is differentfrom the preceding corrected air/fuel ratio A/F(n-1) in step 51, thecontrol system proceeds to step 55, checks the opening position θ of thethrottle, and determines whether the engine is in an idling statecondition or not. For instance, if the opening position is not largerthan 2 degrees, the control system determines that the engine is idling.In step 56, the control system determines whether the gear shift leverswitch Isw(n) has been changed. That is, when the operation checks themotion of the gear shift lever, it is effective to the change of theair/fuel ratio, because the state of engine is limited to stopping orgear changing. In step 57, the control system determines whether thesignal indicative of gear changing FlgI, is 1 or not. When the signal is1, it becomes possible to change the air/fuel ratio in synchronism withthe torque variation in the speed changing, and the torque variationaccompanied by the change of the fuel ratio can be prevented. Wheneither one of step 55 through step 57 is YES, the control systemproceeds to step 58, calculates the corrected fuel injection coefficientk1 by f4 A/F(n)! in synchronism with the change period, and changes theair/fuel ratio to a new target air/fuel ratio. Further, the controlsystem carries out A/F(n-1)=A/F(n) in step 5g and outputs the correctedfuel injection coefficient k1 which has been calculated in step 58, instep 54.

FIG. 11 is a control flow chart in case wherein a traffic jam and anuphill or a downhill condition are overlapped. For instance, when atraffic jam is caused on an uphill road, an engine output is required incorrespondence to the uphill, and it is necessary to cope with it by avariable air/fuel ratio. First, in step 60, the control system reads atraffic jam signal JAM and a road incline β. In step 61, the controlsystem determines whether a traffic jam is caused, that is, whether JAMis 1 or not. When JAM is 1, the control system proceeds to step 62 andcarries out the determination of the traffic jam flag as FlgJ=1. WhenJAM is not 1, the control system proceeds to step 63 and carries out thedetermination of the traffic jam flag as FlgJ=0. Next, the controlsystem determines whether the road incline β is not smaller than, forinstance, 0.5%. When the road incline β is smaller than 0.5%, thecontrol system determines that the road is a flat road or a downhillroad and the air/fuel ratio had better be a lean mixture of about 24. Bycontrast, when the load incline β is not smaller than 0.5%, it isnecessary to change the air/fuel ratio in accordance with the incline.Therefore, when the road incline β is not smaller than 0.5%, the controlsystem proceeds to step 65 and caries out the determination of theuphill flag as Flg β=1. When the road incline β is smaller than 0.5%,the control system proceeds to step 66 and carries out the determinationof the uphill flag as Flg β=0. Further, in step 67, the control systemdetermines Flg J AND Flg β. When the determination is true, the controlsystem proceeds to step 68, and when the determination is false, thecontrol system proceeds to RETURN. When the determination is true, thetraffic jam and the uphill road are overlapped. Therefore, in step 68,the control system calculates the corrected air/fuel ratio A/F by acorrected incline air/fuel ratio table shown in FIG. 11 and a functionf5 (β) of the road incline β. Further, in step 69, the control systemcalculates the corrected fuel injection coefficient k1 by using thecorrected air/fuel ratio A/F which has been calculated in step 68, andoutputs it in step 70.

FIG. 12 shows a corrected air/fuel ratio with respect to the roadincline in case of a traffic jam. In a traffic jam on a road which is ina range from a flat road to a minus incline, the engine output is notconsiderably needed, and the air/fuel ratio of about 24 is sufficient.By contrast, under the uphill incline condition, the engine output whichis required according to the angle of incline, increases. Accordingly,it is necessary to reduce the air/fuel ratio and to form a rich mixture.The actual fuel cost performance can be promoted by the above control.

According to the present invention, the air/fuel ratio changes at anytime in accordance with the change in the running environment.Therefore, it becomes possible to effectively utilize the engine outputand further the actual fuel cost performance is promoted. The switchingof the air/fuel ratios is always performed in accordance with a runningenvironment other than a steady state condition such as speed changing,stopping, idling, shift lever operation or the like. Therefore, theunpleasant feeling by the torque variation accompanied by the change inthe air/fuel ratio. Accordingly, the reduction of fuel cost and thepromotion of drivability can be achieved.

What is claimed is:
 1. A control apparatus for a vehicle having anengine, a throttle valve controlling an amount of air sucked into saidengine, and an accelerator pedal controlling an opening of said throttlevalve, comprising:controller for delivering a control signal whichcontrols said opening of said throttle valve based on a stroke of saidaccelerator pedal; and at least one outer environment detector fordetecting an outer environment information of said vehicle; wherein saidsignal delivered from said controller is corrected by a value whichindicates said outer environment information detected by said outerenvironment detector.
 2. A control apparatus for a vehicle according toclaim 1, wherein said outer environment information is a distance from aforward vehicle.
 3. A control apparatus for a vehicle according to claim1, further comprising:memory for storing data which indicates a controlamount of said throttle valve in relation to said stroke of saidaccelerator pedal.
 4. A control method for a vehicle having an engine, athrottle valve controlling an amount of air sucked into said engine, andan accelerator pedal controlling an opening of said throttle valve, themethod comprising the steps of:detecting an outer environmentinformation of said vehicle; and delivering a control signal whichcontrols said opening of said throttle valve based on a stroke of saidaccelerator pedal and said detected outer environment information.